Eberhardt’s first assignment was with Infantry Regiment No. 93, situated at Zerbst from April 1874 until July 1882. He then served in the 3. Guard-Regiment zu Fuß at Berlin from July 1882 all the way until June 1890. During this time, he was promoted to Oberleutnant in 1883 and Hauptmann in 1889. From here, he worked on the General Staff in Berlin from June 1890 until October 1891.

Eberhardt was the Chief of Staff for the 8. Infantry Division at Erfurt from October 1891 to February 1894. He worked at the Prussian War Ministry February 1894 until April 1898, and in the first year of his service here, he was promoted to Major. Eberhardt was then appointed commander of the Grenadier-Regiment “Prinz Karl von Preußen” which was the 2. Brandenburger Nr.12 situated at Frankfurt an der Oder from April 1898 to September 1900.

He worked on the General Staff in Berlin from September 1900 through February 1903. Eberhardt became Chief of Staff for the X. Army Corps at Hannover in February1903; promotion to Oberst came in the same year, and the stint at the X. Corps lasted only until May 1904. Then came leadership of the Guard-Füsilier-Regiment Nr.1 at Berlin from May 1904 until April 1907. He was also promoted to Generalmajor in 1907. Following this, he was Chief of Staff for the elite Guards at Berlin from April 1907 until January 1911. He was placed in charge of the 19. Infantry Division situated at Hannover from January 1911 until March 1913. Eberhardt was promoted to Generalleutnant in 1911. He was appointed Military Governor of Lower Alsace, with his seat at Strassburg from March 1913 until September 1914.

With experience and knowledge of the terrain in Alsace, Eberhardt was given command of the XV. Reserve Corps in Upper Alsace at the outbreak of war in August 1914, and it was his task to defend this part of Germany from the French invasion. He succeeded in repelling the French attempt to seize Colmar, and pushed them out of nearly all of Alsace except for the Thann-Altkirch sector, which the French held throughout the whole war. The entire force was moved to Serbia. Eberhardt remained in command of this force all the way until October 1916, during which time his reserves were thrown into the Verdun sector.

Eberhardt was then selected to command the X. Reserve Corps in October 1916. He was awarded the Pour le Merite in May 1917, and received the Oakleaves to this prestigious award in September of that year. This was something special, since it was uncommon for a commander to be given such accolades with only a few months between awards. He led this Corps until August 1918.

Then, Eberhardt was appointed to as acting commander of the VII. Army from August until October 1918, replacing General Böhn. After that, he was transferred as the army broke down due to desertions and poor performance. In the beginning of November 1918, Eberhardt replaced Otto von Below as commander of the I. Army, but was in this role only until the army had demobilised in December. After this, Hindenburg sent him to East Prussia to take command of the Culmerland defense forces and thwart any Polish attempts to seize East Prussia. In spring 1919, he was ordered to withdraw all military personnel beyond the Soldau sector and the Polish army took control of this swath of West Prussian territory.